This thread is apparent, but apparently no one noticed it. - !!!!!!!

Question

Does the question writer mean to ask if a thread is "showing"? The question is not IMO stated in idiomatic English. I can't make the question make sense even if the thread in question is an email thread. Maybe I'm being picky.........

Answer

Yes, I think the problem is that in English we only use apparent for abstract nouns - "no apparent reason", "an apparent danger" etc. So it should probably be translated as "visible", or maybe your suggestion of "showing" would work in this case. But that would spoil the word play of the original - 
Ce fil est apparent, mais apparemment  personne ne l'a remarqué.

Answer

Bonjour Max !
Indeed, "showing" would be more colloquial here, and thanks to you, it's now been updated :)
Merci et bonne journée !